Validation of the NeQuick 2 and IRI-2007 models in East-African equatorial region

This paper examines the performances of NeQuick 2 and IRI-2007 ionospheric empirical models in describing the monthly median characteristics of the equatorial region ionosphere. This is carried out by comparing the vertical total electron content (vTEC) obtained from ground Global Positioning System (GPS) receivers and NmF2 obtained from digisonde with the corresponding values computed using these models. Four years worth of data have been considered in this study. We have shown that the performances of both models are better during the medium solar activity period than low solar activity period. The present investigation has depicted that both models overestimate the observed vTEC during low solar activity period. The modeled and experimental NmF2 has shown good agreement; but the modeled and experimental vTEC has shown significant discrepancy. This discrepancy is shown mainly due to inadequately computed ionospheric slab thicknesses using IRI-2007 and NeQuick 2. However, the chi-square test showed that both models are describing the observed vTEC with 99.9% of confidence level except in the time intervals when the double peaks of modeled vTEC are obtained. In addition, we have shown that both models have a relatively minimal mismodeling during the December solstices.